For more than a decade, Anna von Hausswolff has been bringing the sound of pipe organs to rock fans. But Roman Catholic extremists have tried to stop her playing shows in churches.When Anna von Hausswolff, an acclaimed Swedish songwriter and organist, first heard that a conservative Roman Catholic website was calling her a satanist and demanding a concert boycott, she and her team laughed it off.“We thought it was hilarious,” von Hausswolff, 35, recalled in a recent interview. “The whole day we were laughing,”The site, Riposte Catholique, was firing its readers up ahead of a concert of von Hausswolff’s epic pipe organ music at a church in Nantes, a city in the west of France. Some of her fans were goths, the site said, and her songs were “more a black Mass than music for a church.” A music blogger had called her “the high priestess” of “satanic harmonies,” the site noted, and conservative Roman Catholic groups noticed that, on the track “Pills,” she sings, “I made love with the devil.”“We said, ‘This is such a great P.R. campaign,’” Von Hausswolff said. “I mean, ‘the High Priestess of satanic art.’ Wow!”But as soon as she arrived at the church in Nantes, the joking stopped. Outside were about 30 young men, most wearing black jackets and hoodies, protesting the show, Von Hausswolff said. The concert’s promoter told her that some men had just broken into the venue, trying to find her.Soon, there were 100 people blocking the church’s entrance. Von Hausswolff sat in the richly painted church, staring up at the organ that she’d hoped to play, listening to protesters chanting and banging on the doors outside as her fans shouted back at them.“There was a primal part of me that told me I was not safe,” she said. “I wanted to get out.” She canceled the show.In recent years, disagreements between conservatives and liberals over issues like gay marriage and abortion have become increasingly heated in parts of Europe. Von Hausswolff’s experience is an example of another tension point in the continent’s culture wars: In some countries, a small minority of Roman Catholics regularly protests art it considers blasphemous.Initially, when the campaign against her was just online, Anna von Hausswolff laughed off the accusations of Satanism. Ines Sebalj for The New York TimesCéline Béraud, an academic who studies the sociology of catholicism in France, said in a telephone interview that extremists had staged protests against artworks and plays in the country for the past 20 years. “It comes from a well organized minority who’re very good at getting attention in the media,” Béraud said.One of their regular targets is Hellfest, a rock music festival held every year close to Nantes. In 2015, a group of protesters broke into the site and set fire to some of the festival’s stage sets. Since then, protesters have regularly doused the festival site’s fields with holy water. Hellfest’s communications manager, Eric Perrin, said in an email that staff members recently found 50 gold pendants depicting the Virgin Mary scattered around the site. Since playing a real pipe organ in concert almost always means playing in church, von Hausswolff’s tour problems didn’t end when she left Nantes — even though some French bishops had issued statements of support. In Paris, she was scheduled to play the grand organ at St.-Eustache, a church widely considered a jewel of the French Renaissance, but after its priest was deluged with complaints, she instead performed a secret show at a Protestant church near the Arc de Triomphe.In December, protestors gathered outside a von Hausswolff concert in Brussels. “That was fine,” Von Hausswolff said. “They weren’t screaming or banging on doors.”Laurie Dieffembacq/Belga, via Agence France-Presse — Getty ImagesLater, in Brussels, about 100 people protested outside her show at a Dominican church, taking a more peaceful approach than their French counterparts and moving away from its doors when asked by police. At Nijmegen, the Netherlands, just two protesters appeared, standing quietly outside while holding signs with the message “Satan is not welcome.”Von Hausswolff is not someone you would expect to cause such a stir. She grew up in Gothenburg, Sweden, and said her childhood was “very creative.” (Her father, Carl Michael von Hausswolff, is a composer and performance artist.)As a teenager, she sang in a church choir, and dreamed of becoming a musician, but ended up training as an architect. Her music career only took off in 2009 when, age 23, she released a demo of piano songs called “Singing from the Grave” that quickly found a fan base in Sweden thanks to her soaring vocals. She was frequently compared to the English pop star Kate Bush.After an organ builder told her she could make beautiful pipe organ music, she gave it a go, she recalled, trying out the organ in Gothenburg’s vast Annedal Church. “When I reached the lowest note, I couldn’t believe my ears,” Von Hausswolff said. “I felt it through my whole body.”She’s since explored what the instrument can do across five albums, sometimes pairing it with a rock band and at other times performing solo. Her most recent, released this month, is a live album recorded at the Montreux Jazz Festival in Switzerland.Hans Davidsson, an organist who helps von Hausswolff probe the instrument’s capabilities, said that she “explores the organ with open ears, eyes and senses,” and had developed her “own musical language.” Her music was inspiring to many classical organists like him, he added. “It’s fortunate for us that she chose the organ,” he said.In the interview, von Hausswolff, who was wearing Christmas leggings covered in cartoon reindeer in Santa hats, denied she was a satanist. Von Hausswolff declined to say what her 2009 track “Pills” — in which she sings of satanic lovemaking — was about, since songs should be left open to interpretation, she said. But, she added, “If you’re asking me if I literally had sex with the devil, the answer is, ‘No.’”“I’m there to present my pipe organ art so that it hopefully can invoke deeper thought in people,” Von Hausswolff said of her work.Ines Sebalj for The New York TimesAs much as she was happy to joke about the accusations, the incidents last month had left a mark. She still felt scared by the French and Belgian protests, she said, and was also worried that churches might think twice about letting her play their organs, so as to avoid complaints.“I’m not a good Christian and never will be,” said von Hausswolff, adding that she saw herself as agnostic. “But I’m there to present my pipe organ art, so that it hopefully can invoke deeper thought in people.”She was already planning more church tours, she said. As long as she was welcome, she added, “I will go there, and I will play my music.” More